The present disclosure relates to a cascade heat pump.
In general, heat pumps are apparatuses for air-conditioning an indoor room or refrigerating or freezing foods using a refrigerant circulating into a refrigerant cycle including a compressor for compressing the refrigerant, a condenser for condensing the refrigerant discharged from the compressor, an expander for expanding the refrigerant passing through the condenser, and an evaporator for evaporating the refrigerant expanded by the expander.
Recently, to improve efficiency of a system, a cascade heat pump including a first refrigerant cycle in which a first refrigerant circulates and a second refrigerant cycle in which a second refrigerant circulates to heat-exchange the first refrigerant with the second refrigerant through a refrigerant heat exchanger is being developed.
In this case, the first refrigerant cycle may be used as a cycle for air-conditioning an indoor room, and the second refrigerant cycle may be used as a cycle for refrigerating or freezing foods. Here, the first refrigerant may be evaporated in the refrigerant heat exchanger, and the second refrigerant may be condensed to heat-exchange the first refrigerant with the second refrigerant.
Also, a flow direction of the first refrigerant circulating into the first refrigerant cycle may be switched according to the switching of a cooling/heating operation mode. However, the second refrigerant circulating into the second refrigerant cycle may circulate always in the same direction.
In the cascade heat pump which realizes the air-conditioning operation or the refrigerating or freezing operation according to the related art, the refrigerant circulating in the refrigerant cycle is compressed using one compressor. Thus, a compression ratio may be decreased, and efficiency of the cascade heat pump may be reduced.